To conserve energy, it has been found desirable to provide a substantial thickness of insulation in the walls, roofs, and other parts of a structure. While such can be readily achieved by using deeper framing members, such as 2×6 lumber instead of 2×4 lumber for studs, footers, plates, and headers of the frame, this significantly increases the cost of materials. An alternative to the use of 2×6 timbers is to use metal 2×6 members which are typically C-channels that have a web portion with passages therethrough providing openings that result in a constricted cross section and elongated heat transfer path to reduce heat conduction between the terminating surfaces of the member. One such member is taught in U.S. Pat. No. 4,016,700. The use of metal framing may cause additional difficulties in that covering the frame with a surfacing material may require alternative fastening techniques and thus not be fully compatible with standard fabrication techniques used for building stick structures. Also, the use of deeper framing members is not practical when modifying an existing structure to provide increased insulation. A further concern, when larger timbers are used, is that the wooden structural members can provide a thermal bridge between interior and exterior walls, reducing the overall insulating characteristics of the structure. Similar concerns apply for insulating other parts of the structure, such as floors and roofs.
One attempt to overcome these problems is to provide extenders that can fasten to the structural members of the frame to provide increased depth, such as taught in U.S. Pat. No. 4,466,225. The '225 patent teaches an extender formed from sheet metal stamped into a J or C shape, with tabs that serve to align the metal extender against the stud. When so aligned, the extender can be secured to the stud with fasteners such as nails, and provides a mounting surface to which wall surfacing material such as drywall panels can be fastened, this mounting surface being spaced apart from the stud by a certain amount, typically two inches to provide a 2×4 stud with the effective depth of a 2×6 stud. While the '225 extender allows a greater thickness of insulation to be placed in the frame, the use of thermally conductive sheet metal for the extender creates a thermal path that may significantly decrease the benefit of the increased thickness of insulation. This could be particularly true in structures where metal studs are employed.
The embodiment shown in FIG. 1 of the '225 patent has a further deficiency in that it does not provide sufficient passage therethrough to allow ready access through the completed structure for wiring and/or blown-in insulation. While the embodiments shown in FIGS. 2 and 3 of the '225 patent would provide such access, the use of multiple discrete elements complicates construction, since these individual elements must be separately positioned on the stud and fastened thereto. A further complication is that the resulting mounting surface is not continuous, requiring greater care when fastening the wall surface material to the extenders.